Many electronics circuits depend on reliable heat dissipation systems to ensure stable operation and efficiency. Thermal excitement in electrical systems leads to increased noise. Without an effective heat dissipation system, failure or unstable operation is possible.
Conventional heat dissipation systems depend on one or more of the following strategies: passive convection operating directly on the heat producing components of the electronic device; addition of an active cooling solution, such as a fan or liquid cooling system; placement of a heat sink in conductive contact with the heat producing components, such that the heat sink and the components are then in thermal equilibrium and both dissipate heat through convective means.
To offer higher capacity heat transfer, new heat dissipation equipment must be more efficient. It is difficult for air-cooled heat sinks to grow in size, because equipment manufacturers are under tremendous competitive pressure to maintain or diminish the size of their equipment packages, all the while filling them with more and more components. In addition, larger heat sinks typically will increase the cost of the heat sink element. Thus, competitive heat dissipation equipment must be relatively compact in size and must perform at levels sufficient to prevent high-performance components from exceeding their operational heat specifications.
Conventional heat dissipation systems are at odds with these requirements. Heat sinks and active cooling solutions are bulky and require additional space within the device package. Even passive convective cooling requires the allotment of space within the device to allow for air flow.
Prior work in the art has shown that a solution analogous to a heat sink need not require additional space within the device package. United States Patent Publication No. 2002-0092160 reveals a device wherein the structural frame is composed of a heat conductive material and is thermally coupled to the electronic components therein, whereby the frame and electronic components are at thermal equilibrium and passive convective cooling of the entire system occurs more rapidly than it otherwise would.
This type of cooling system, relying on heat dissipation through passive convection, is acceptable for low power, battery-operated, portable applications. Higher power electronics create more heat, and dissipation thereof through the exterior of the device package could presumably allow the exterior surface to reach an unsafe temperature. For the same reasons, attaching any form of heat sink to the exterior of a device would not only increase the package bulk, but allow for possible user contact with a hot element used.
Traditional AC/DC power converters, such as for cellular telephones typically include a plastic housing with air or other insulation surrounding the electronic power convertor circuit. For cooling, such circuits have relied on large device packages and, in some cases, the presence of vents to facilitate passive convective cooling of an enclosed circuit board including a plurality of electronic components mounted on a PCB. This strategy results in a device inconveniently large in size. Furthermore, the convective means of cooling circuitry in an enclosed space, even with vent holes, has poor efficiency, resulting in a high equilibrium operating temperature for the electronic device.
This construction method results in large device packages for several reasons. Conventional power conversion circuits include primary and secondary circuits: a primary circuit is connected directly with the AC power input to be converted and power is output through the secondary circuit. Safety regulations require a minimum distance of 6.4 mm between the secondary and primary circuits through air. Further, because government regulations mandate that operating temperatures in such devices not exceed a certain range above the ambient temperature, smaller device packages are not feasible using prior art techniques: a package having a large surface area is often the only means of achieving the needed heat dissipation. Devices constructed according to prior art techniques to have a certain size. This is true since even low powered devices, which might obtain sufficient heat dissipation through a small package, because they are required to meet the through-air requirement of a 6.4 mm spacing.
In view of this, users must carry an undesirably large power converter to charge their cellular telephone. It is further well known in the art that relatively higher operating temperatures result in relatively higher incidence of device failure and in less efficient operation.
Because current cooling system designs necessitate large device packages, especially in power conversion devices, many current power converter designs are bulky and inconvenient. Compare the power adapters designed to charge cellular phone batteries with a standard AC power plug. The typical cellular telephone power adapter employs a bulky housing to hold the plug blades and the power conversion circuitry. The relatively large size of the power adapter is necessary because of the heat dissipation requirements outlined above. Exclusive of those requirements, it is apparent that a smaller, more compact device packaging would be advantageous for such power adapters. The advantages of such a construction are especially clear since cellular phone adapters are necessarily portable and thus stand to benefit substantially from a sleeker device packaging.
In view of the above, there is a demonstrated need for a cooling system capable of handling the large heat loads created in power electronics, but that also allows for compact device packaging and does not present a hazard to the user. This need is especially apparent in the field of power converter manufacturing, where current cooling systems preclude the creation of a compact power converter that is both efficient and reliable.